Transformer cooling system control



United States Patent TRANSFORMER COOLING SYSTEM CONTROL Richard L.Schwab, Hickory Township, Mercer County, Pa., assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation ofPennsylvania Application March 7, 1958, Serial No. 719,808

8 Claims. (Cl. 323-44 This invention relates to transformers and, moreparticularly, to means for protecting air-cooled transformers fromexcessive temperatures.

In Patent No. 2,640,101, issued to A. V. Hughes, and :assigned to thesame assignee as the present application, protective means is providedfor electrical apparatus, such as an air-cooled transformer, theprotective means including a control device operative in response topredetermined conditions of the transformer for actuating cooling meansupon the occurrence of a predetermined operating condition andthereafter actuating a signalling :device upon the occurrence of otherpredetermined op- :erating conditions of the transformer, such as thefailure :of the cooling means to operate or when the cooling means isoperating inefiiciently. More particularly, the control device isresponsive to both the predetermined heating effects of current flowingin the windings of the .transformer and the predetermined temperatures.of air currents which pass over the windings of the transformer. .Adisadvantage of the above protective means is that it does not includemeans for actuating the signalling device during periods when thecooling means is operating. This is because the temperatures to whichthe con- .trol device in the above protective means responds to :actuatethe signalling device during self-cooled operation are higher than thetemperatures to which the control device responds to actuate the coolingmeans. In order to provide suitable means for actuating the signallingdevice during periods in which the cooling means is operating, the meansfor actuating the signalling device must respond to temperature duringthe latter periods which are less than the temperatures to which thecontrol device in the above protective means responds to actuate thecooling means. This is because the cooling means imparts a (coolingeffect not only to the windings of the transformer but also to anythermally responsive control device included in a protective means. Itis therefore desirable to provide protective means for a transformer ofthe type described for controlling the operation of the cooling meansand for actuating a signalling device upon the occurrence ofpredetermined operating conditions of .the transformer regardless ofwhether the cooling means is operating.

An object of this invention is to provide a new and improved air-cooledtransformer having protective means for controlling the operation of thecooling means associated with the transformer and for indicatingpredetermined operating conditions of the transformer.

Another object of this invention is to provide protective means for anair-cooled transformer including thermally responsive devices foractuating cooling means in response to a predetermined operatingcondition of the transformer and for actuating signalling means inresponse to other predetermined operating conditions of the transformerboth before and after said cooling means is actuated.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the acc0mpanying drawing in which the single figure is aview in side elevation, partly in section and partly diagrammatic, ofcircuits and apparatus illustrating one embodiment of this invention.

Referring to the drawing, this invention is illustrated by reference toan air-cooled, air-insulated transformer 1 which is of the generalconstruction described and claimed in Patent No. 2,295,415 to G. R.Monroe, issued Septemher .8, 1942, and assigned to the same assignee asthis application. As illustrated, the transformer 1 comprises a casing 2which may have ventilated openings in the side walls (not shown) forproviding free access of the surrounding air to contact a core structure3 and winding structure thereon, disposed within the casing. The corestructure 3 is provided with two vertically positioned winding legs .4and 5 connected to two horizontal yoke portions clamped between channelmembers 6 at the top of the structure and between channel members 7 atthe bottom of the structure, respectively, and held in .position by thebolts 8 for clamping the channel members together. A pair of upperpressure plates or rings 9 and a pair of lower support members 10,respectively, are pro vided for assisting in holding a high-voltagewinding 11 and a low-voltage winding 12 disposed internally thereof intheir proper positions about the winding legs 4 and 5 of the corestructure 7. The rings 9 and support members 10 are ,of a spiderconstruction (not shown) to facilitate passage of air therethrough toand from the windings 12 and 11.

The low-voltage winding 12 comprises a plurality of cylindrical coils 13separated by spacers 14 and wound about a central tube 15, the tube 15and the coils 13 extending from the lower support members 10 to theupper pressure plates 9. The high-voltage winding 11 comprises aplurality of flat or disk-type coils 16 separated by the spacers 17 ofinsulating material, such as porcelain, the spacers 17 being arranged invertical columns between adjacent coils and the spacers 14 beingarranged in horizontal rows between adjacent coils. The spacers 17 and14 are spaced about the circumference of ,thewindngs 11 and 12,respectively, in a manner to provide openngs in the windings 11 and 12radially between the ad acent coils, the spacers 14 providing openings74 between the coils 13 of the winding 12 which extend from the lowersupport members 10 to the upper pressure plates 9 for permitting thefree movement of air currents upwardly between the .coils 13. Thewindings 11 are positioned between the blocks 18 between the supportmembers 10 and the lower end of the windings 11 and between the pressurerings 9 and the upper end of the windings 11 .to assist in clamping thecoils of the windngs 11 firmly in place between the members 9 and 10- Inorder to provide for forced cooling of the core and coil assembly, a fan19 is disposed at one end of a housing 20 for operation when thetransformer 1 is operating under a predetermined overload condition. Asillustrated, the housing 20 is positioned beneath the coil asasembly ofthe transformer 1, the upper horizontal surface of the housing 20constituting the support members 10 extending below the coil assemblyfor supporting the coil assembly as described hereinbefore, the lowerhorizontal surface of the housing 20 constituting a lower plate member21 for supporting the channel member 7, one end of the housing 20terminating in an opening 22 for receiving the fan 19, the housing 20being enclosed by supporting side walls 23-. The plate member 10 isformed with a central opening (not shown) for receiving the lower endsof the winding legs 4 and 5 of the core struc ture 3, as viewed in thedrawing, this opening in cooperation with the spider construction (notshown) of the plate permitting air currents forced upwardly by operationof the fan 19 to enter into the region occupied by the coil assembly forcirculation thereabout to cool the coil assembly.

In order to control the operation of the fan 19 which is disposed foractuation upon the occurrence of a predetermined operating condition ofthe transformer 1 for cooling the coil assembly thereof and to alsocontrol the operation of the signalling device 24 which may be a light,bell or other suitable device disposed for actuation thereafter toindicate predetermined operating conditions of the transformer 1 bothduring self-cooled and fan-cooled operation, a first control .device 25and a second control device 125 are disposed within the casings 26 and126, respectively, which are preferably mounted adjacent to each otheratop the coil assembly of the transformer 1 on one of the pressureplates 9 and over one of the spider openings 27 therein. The firstthermally responsive control device 25 and the second thermallyresponsive control device 125 are of the general construction andoperate similarly to the device described and claimed in Patent No.2,169,586 to M. G. Leonard, issued August 15, 19 39, and assigned to thesame assignee as this application. In general, the first control device25 is designed to respond to higher temperatures than the second controldevice 125.

The thermally responsive bimetal elements 28 and 128 are included in thecontrol devices 25 and 125, respectively, and comprise a part of acircuit which extends from one terminal of a current transformer 29disposed in, relation with a conductor 30 of the load circuit of thetransformer 1 through the bimctal 28, the conductor 31, the energizingWinding 32 of a relay 33, through the con ductor 34 and the birnetal 128to the other terminal of the current transformer 29. The bimetals 28 and128 are responsive to both the predetermined heating effects of currentinduced in the winding of the current transformer 29 which is a measureof the current flowing in the load circuit of the transformer 1 and thepredetermined temperatures of air currents which move upwardly from thecoil assembly of the transformer 1 into the casings 26 and 126 of thefirst control device 25 and the second control device 125,respectively.

The heating of the bimetals 28 and 128 due to the current flowtherethroug'h that is proportional to the load current onthe transformer1 reflects immediately in the control devices 25 and 125 any change intheiloading of the transformer, which might overheat and endanger thetransformer during self-cooled and fan-cooled operation, respectively.Thus, the bimetals 28 and 128 are disposed for movement to predeterminedpositions to the right when the low voltage winding 12 hasbecomeoverheated by the presence of dangerous overloads on the transformer 1during self-cooled and fan-cooled operation respectively of thetransformer 1 which cause currents of heated air to rise upwardlybetween the coils 13 into the casings 26 and 126 of the thermallyresponsive control devices 25 and 125, respectively.

In order to provide for proper operation of the fan 19, the energizingwinding 32 of the relay 33 is included in the circuit describedhereinbefore. The winding 32 is therefore, responsive to cun'ent whichis proportional to the load current of the transformer 1 and is designedand adapted to be so energized thereby when the load current of thetransformer 1 reaches a value slightly higher than the value of therated full load current of the transformer l as to actuate the normallyopen contact member 35 thereof to a circuit closing position. When thecontact member 35 is actuated to the circuit closing position, a circuitis established which extends from the power line conductor 36 throughthe conductor 37, an automatic-manual selector switch38, shown as beingin the automatic position, through the contact member 35 and theconductor 39 to a fixed contact member 40 of the first control device25.

In order to control the sequential operation of a plurality ofcontactors to thereby control the operation of the fan 19 and the signaldevice 24 during both selfcooled and fan-cooled operation of thetransformer 1, a pair of pivotally mounted switch operating members 41and 42 are included in the first control device 25 within the casing.26,and a pair of pivotally mounted switch operating members 141 and 142 areincludedin the second control device 125 within the casing 126. As thetransformer 1 heats up initially,.the lower end of the member 1410f thesecond control device 125 is disposed to be moved bythe bimetal 128 uponthe occurrence of a predetermined movement of the bimetal 128 to theright to effect movement of the free end of the member 141 to the left.A contact member. 143, carried by the member 141 at thefree end thereof,is thereby moved away from engagement with a cooperating fixedcontactmember 140 for opening the circuit which extends from the power lineconductor 48 through the conductor 154, thej contact members 140 andl43, the conductor 152 te anormallyopen contact rnemher 1500fthecontactor 46 which is c'onnected in series circuitrelationship withthe energizing winding 122 of the contactor 120. Thus, whenever thecontact members 140 and 143 are disen gaged, the energizing winding 122of the contactor 126 will .be deenergized for reasons which will beexplained hereinafter. As the transformer 1 heats up still further,thepivotaJIy mounted switch operating member 142 ,is disposed to beactuated by a further predetermined movementof the bimetal 128 to theright for effecting movementof the free end of the member 142 to theleft. A

contact member 168 carried by the pivoted member 142 at the free end vthereof is thereby moved into engagemerit with a fixed contact: member169. The engagement of contact members 168 and 169 establishes a circuitextending from the conductor 71 at one side of the energizingwinding 58of the contactor 57 through the contact members 169 and 168, through theconductor 156 toa normally open contact member 123 of the contactor forreasons which will be explained hereinafter.

As previously described, the first control device 25'responds totemperatures which are higher than the temperatures to which the secondcontrol device 125 responds. As the transformer 1 heats up stillfurther, the switch operating member 41 of the first control device 25is disposed to be engaged by the bimetal 28 upon the occurrence of apredetermined movement of the bimetal 28 tothe right to effect movementof the free end of the member 41 tothe left. A contact member 43carried'by the member 41 at the free end thereof is thereby movedengagement with a fixed contact member 48 for establishing a circuitextending from the power line conductor 36 through the conductor 37, theswitch 38, through the contact member 35 whenever the relay 33 isenergized, the conductor '39, the contact members 40 and 43,

the conductor 44, the energizing winding 45 of a contact'or 46andthrough' the conductor 47 to the power line conductor 48. The winding45 of the contactor 46 is, therefore, connected ac'ross the power lineconductors 36 and 48, and is thereby energized to simultaneously effectmovementof a plurality of normally open contact members 49, 50, 51 andthereof to circuit closing positions.

.The movement of the contact members 50 and 51 of the contactori46 tocircuit closing positions elfects energization of the fan motor 52through a circuit extending from the power line conductor 36 throilghtheconductor 53, the contact member 50, the conductor 54, the fan vmotor,52, the conductor 55, the contactmernber 51 and the conductor 47 to thepower line conductor 48, thus effecting the energization of the.fanmotor SZL t operate the fan 19. The movement pf the, contact niember4 9 effects establishment of a holding ci'rcuit'for the winding 45 ofthe contactor 46 which is disposed to thereafter maintain theenergization of the fan motor 52. The holding circuit extends from thepower conductor 36 through the conductor 37, the switch 38, the contactmember 35, the conductor 56, the contact member 49, the energizingwinding 45 of the contactor 46 and the conductor 47 to the lineconductor 48. The movement of the contact member 150 to a circuitclosing position permits energization of contactor 120 whenever thecontact members 140 and 143 of the second control device 125 are engagedthrough a circuit which extends from the conductor 36 through theconductor 53, the energizing winding 122 of the contactor 120, throughthe contact member 150, the conductor 152, the contact members 140 and143, and through the conductor 154 to the power line conductor 48.

The holding circuit is necessary for the effective operation of theprotective means or system for, as the fan 19 begins operation, air isforced upwardly thereby from the housing 20 and is circulated about thearea occupied by the heated low voltage windings 12 to force the airheated by the windings 12 upwardly into the casings 26 and 126 for notonly cooling the low voltage windings 12 but for also cooling thethermally responsive bimetal elements 28 and 128. It is readily apparentthat such a result is inevitable, for the air actuated by the fan 19rises upwardly from the low voltage windings 12 into the casings 26 and126 to effect such cooling of the bimetal elements 28 and 128,respectively. The thermal action of the cooler air on the bimetalelement 28 tends to cause the bimetal element 28 to operate to reversethe initial sequence of operations whereby the free end of the switchoperating member 41 tends to move to the right to disengage the contactmembers 40 and 43 and interrupt the energizing circuit for theenergizing winding 45 of the contactor 46. However, since the holdingcircuit for the energizing winding 45 has been established, thecontactor 46 is maintained in its energized circuit closing position tothereafter maintain operation of the energizing circuit for the fanmotor 52 independently of the position of the bimetal 28. However, whenthe load current on the transformer 1 is reduced to a predeterminedvalue which permits safe operation of the transformer 1, the currentflow through the winding 32 of the relay 33 is insufficient to maintainthe relay 33 in a circuit closing position, and the contact member 35 ofthe relay 33 drops to a circuit interrupting position to interrupt theholding circuit for the winding 45 of the contactor 46.

In similar fashion, after the fan 19 begins operation, the thermalaction of the cooler air on the bimetal element 128 after a time delaytends to cause the bimetal element 128 to operate to reverse the initialsequence of operations whereby the free end of the switch operatingmeans 142 tends to move to the right to disengage the contact members168 and 169 and the free end of the switch operating member 141 tends tomove to the right to move the contact member 143 into engagement withthe contact member 140, thus energizing the contactor 120 through thecircuit which extends from the power line conductor 36 through theconductor 53, the energizing winding 122 of the contactor 120, thecontact member 150 of the contactor 46, through the conductor 152, thecontact members 143 and 144 and through the conductor 154 to the powerline conductor 48. The winding 122 of the contactor 120 is, therefore,connected across the power line conductors 36 and 48, and is therebyenergized to simultaneously effect movement of the contact members 124and 123 thereof to circuit closing positions. The movement of thecontact member 124 effects establishment of a holding circuit for thewinding 122 of the contactor 120 which extends from the power lineconductor 48 through the conductor 47, through the contact member 124and the contact member 150, through the winding 122 of the contactor120, through the conductor 53, and back to the power line conductor 36.The movement of the contact member 123 of the contactor to a circuitclosing position has no effect on the operation of the control circuitso long as the contact members 168 and 169 of the second control deviceare disengaged since the contact member 123 is connected in seriescircuit relationship with the contact members 168 and 169 of the secondcontrol device 125.

In order to control the operation of the signal device 24, anothercontactor 57 having an energizing winding 58 is included in the controlcircuit for the protective means or system. When the transformer 1 isinitially arranged for operation, the winding 58 is placed in a normallyenergized condition by manual actuation of a start-reset switch 59 to acircuit closing position for establishing a circuit extending from theline conductor 36 through the conductor 37, the switch 59, the conductor60, the winding 58 of the contactor 57, the resister 61 and theconductor 47 to the line conductor 48 to thereby connect the winding 58across the line conductors 36 and 48 for energizing the winding 58. Suchenergization of the winding 58 effects the movement of a pair of contactmembers 62 and 63 of the contactor 57 to circuit interrupting andcircuit closing positions, respectively. The movement of the contactmember 62 to a circuit interrupting position interrupts a signal circuitextending from the line conductor 36 through the conductor 64, thesignal device 24, the contact member 62, and the conductor 65 to theline conductor 48 to thereby maintain the signal device 24 in aninoperative condition until predetermined operating conditions of thetransformer 1 effect the energization thereof. The movement of thecontact member 63 to a circuit closing position establishing a holdingcircuit extending from the line conductor 36 through the conductors 53and 66, through the contact member 63, the conductor 67, the winding 58of the contactor 57, the resistor 61 and the conductor 47 to the lineconductor 48 to thereby maintain the energization of the winding 58 ofthe contactor 57 until such time as the operating conditions of thetransformer 1 effect deenergization of the winding 58 for effecting theenergization of the signal device 24 by means of an operation which willbe described hereinafter.

In order to effect the deenergization of the contactor 57 during theself-cooled operation of the transformer 1, the pivotally mounted switchoperating member 42 of the first control device 25 is disposed to beactuated by a further predetermined movement of the bimetal 28 to theright for effecting movement of the free end of the member 42 to theleft. The contact member 68 carried by the pivoted member 42 at the freeend thereof is thereby moved into engagement with a fixed contact member69. The engagement of contact members 68 and 69 establishes a circuitextending from the power line conductor 36 through the conductors 53 and66, the contact member 63 normally disposed in the circuit closingposition as described hereinbefore, the conductors 6'7 and 70, theclosed contact members 68 and 69, through the conductor 71, the resistor61 and the conductor 47 to the power line conductor 48. This circuit isdisposed for shunting the normally energized winding 58 of the contactor57 to effect the denergization of the winding 58, thereby causing thecontact members 63 and 62 to drop to circuit interrupting and circuitclosing positions, respectively. The resistor 61 is provided in order toprevent a short circuit between the power line conductors 36 and 48whenever the contact members 68 and 69 are engaged. The movement of thecontact member 62 to the circuit closing position establishes the signalcircuit for energizing the signal device 24, and the movement of thecontact member 63 to the circuit interrupting position interrupts theenergizing circuit for the energizing winding 58 of the contactor 57 tothereafter maintain the deenergization of the winding 58 and'the sesameenergization of the signal device 24. When it is desired to deenergizethe signal device 24, the switch 59 may be manually actuated to thecircuit closing position as was described hereinbefore, A

Inorder to effect the deenergization of the contactor 5.7 after the fan19 beginsoperation, it is necessary that the effect of the thermalaction of the cooler air on the bimetal element 128 cause the contactmembers 146 and 143 of the second control device 125 to return to acircuit closing position and the contact members 163 and 169 to returnto a circuit interrupting position as previously described. After thecontact members 146 and 143 return to a circuit closing position, thecontactor 120 will be energized through a circuit which extends from thepower line conductor 36 through the conductor 53, the energizing winding122 of the contactor 12% the contact member 150 of the contactor 46, theconductor 152, the contact members 143 and 140, and through theconductor 154 to the power line conductor 43. The winding 122 of thecontactor 120 is, therefore, connected across the power line conductors46 and 48 and is thereby energized to simultaneously effect movement ofa pair of contact members 124 and 123 of the contactor 120 to circuitclosing positions. The movement of the contact member 124 to a circuitclosing position effects establishment of a holding circuit for thewinding 122 of the contactor 121 which extends from the power conductor36 through the conductor 3, the winding 122 of the contactor 120, thecontact member 150 of the contactor 46, through the contact member 124of the contactor 120, through the conductors 132 and 47 to the powerconductor 48. The contactor 120 remains energized thereafterindependently of the operation of the contact members 140 and 143 of thesecond control device 125. The movement of the contact member 123 of thecontactor 120 establishes a closed circuit which extends from one sideof the energizing winding 53 of the contactor 57 through the contactmember 123 and the conductor 156 to the fixed contact member 168 of thesecond control device 125.

After the initial effect of the thermal action of the cooler air on thebimetal 128 has returned the contact members 140 and 143 to a circuitclosing position and the contact members 168 and 169 of the secondcontrol device to a circuit opening position, a further increase in theload on the transformer 1 will cause an increase in the temperature ofthe air which is heated by the windings of the transformer 1 and risesinto the casing 126 of the second control device 125. The thermal actionof the heated air will effect movement of the bimetal element 128 to theright to disengage the contact member 143 from engagement with thecontact member 142 Such operation will have no effect on theenergization of the contactor 120 since a holding circuit will havealready been established as previously described. As the transformer 1heats up still further, however, during fancooled operation thepivotally mounted switch operating member 142 is actuated by a furtherpredetermined movement of the bimetal 128 to the right for effectingmovement of the free end of the member 142 to the left. The contactmember 168 carried by the pivoted member 142 at the free end thereof isthereby moved into engagement with the fixed contact member 169. Theengagement of the contact members 168 and 169 now establishes a circuitextending from the power line conductor 36 through the conductors 53 and66, through the contact member 63 normally disposed in the circuitclosing position as described hereinbefore, the contact member 123 ofthe contactor 120, the conductor 156, the contact members 168 and 169,the conductors 158 and '71, the resistor 61, and through the conductor:7 to the power line conductor 48. This circuit is disposed for shuntingthe nornially energized winding 58 during fan-cooled operation of thetransformer 1, thereby causing contact members 62 and 63 to drop tocircuit inter circuit for energizing the signal device 24, and therr'rovement of thecontact member 63 to the circuit interrupting positioninterrupts the energizing circuit for the en ergizing winding 58 of thecontactor 57 to thereafter maintain the ,deenergization of the winding58 and the energization of the signal device 24.

A brief description of the overall operation of the protective system ormeans will serve to illustrate the advantages thereof. Assuming that theload is connected to the transformerl initially and gradually increased,and that the protective means or system is properly arranged for normaloperation, that is, the automatic manual switch 38 has been manuallyactuated to the automatic position and the start-reset switch 59 hasbeen manually actuated to a position for energizing the winding 58 ofthe contactor 57. The air heated by the windings of the transformer 1rises into the casings 26 and 126 and by thermal action effects movementof the bimetal element 128 to the right to cause the switch operatingmember 141 to move the contact member 143 away from engagement with thecontact member 149, thereby preventing energization of the contactor 126until after the fan 19 begins operation and the contact members and 143have returned to a circuit closing position. As the transformer heats upfurther, the bimetal element 128 will move to a predetermined positionfurther to the right for engaging the switch; operating member 142 tomove the contact member 168 carried thereby into engagement with thefixed contact member 169'. The engagement of the contact members 168 and169 will have no effect at this stage of the operation of thetransformer 1 since thecontactor 120 is deenergized, and the contactmember 123 of the contactor 120, which is connected in'series circuitrelation with the contact members 169 and 168, will be in a circuitinterrupting position. a

As the load on the transformer 1 increases to a value slightly above therated full load value of the apparatus, the winding 32 of the relay 33is energized by a current flowing therethrough which is proportional tothe load current of the transformer 1 so as to actuate the contactmember 35 of the relay 33 to a circuit closing position. In addition, asthe transformer 1 heats up still further, the thermal action of the airrising from the windings of the transformer 1 will effect movement ofthe bimetal element 28 of the first control device 25 toward the switchoperating member 41 for engagement therewith to move the contact member43 into engagement with the contact member 40, thereby establishing theenergizing circuit for the winding 45. Such operation effects movementof the contact members 49, 50, 51 and to circuit closing positions forsimultaneously establishing the holding circuit for the winding 45, theenergizing circuit for the fan motor 52 and the circuit extending fromthe winding 122 of the contactor 120 to the contact member 143 of thesecond control device 125, respectively.

As the fan motor 52 begins operation, the fan 19 is rotated thereby forforcing air currents upwardly from the housing 20 into the casings 26and 126 of the first and second control devices 25 and 125,respectively, to thereby effect a cooling action of the bimetal elements2S and 128, respectively, by thermal action. One effect of the thermalaction is to move the bimetal 28 away from the member 41 whereby thecontact member 43 is actuated to a circuit interrupting position. Thefan motor 52 continues to operate the fan 19, however, since the holdingcircuit for the winding 45 has been established to maintain theenergization of the winding 45 of the contactor 46 to thereby maintainthe energizing circuit for thefan motor 52 independently of the positionof the bimetal element 28.

A second effect of the thermal action of the cooling air caused byoperation of the fan 19 is to move the bimetal element 128 of the secondcontrol device 125 to thereby return the contact members 168 and 169 toa circuit interrupting or disengaged position and the contact members140 and 143 to a circuit closing or engaged position in that order. Thereturn of the contact members 140 and 143 to a circuit closing positionenergizes the contactor 120 since the contact member 150 is already in acircuit closing position due to the energization of the contactor 46.Such operation effects the movement of the contact members 124 and 123to circuit closing positions for simultaneously establishing the holdingcircuit for the winding 122 of the contactor 120 and the circuit whichextends from one side of the winding 58 of the signalling contactor 57to the fixed contact member 168 of the second control device 125 tothereby permit the second control device 125 to control thedeenergization of the signalling contactor 57.

If the load on the transformer 1 is further increased during fan-cooledoperation, the thermal action of the heated air from the windings of thetransformer 1 is to move the bimetal 128 to thereby disengage thecontact members 140 and 143. Such operation has no effect since aholding circuit has already been established for the winding 122 of thecontactor 120. As the transformer 1 heats up still further duringfan-cooled operation, a movement of the bimetal element 128 of thesecond control device 125 to a predetermined position further to theright engages the switch operating member 142 to move the contact member168 into engagement with the fixed contact member 169. Engagement of thecontact members 168 and 169 effects the establishment of the circuitwhich shunts the normally energized winding 58 of the contact 57 toeffect the deenergization of the Winding 58. The contact members 63 and62 then drop to circuit interrupting and circuit closing positions,respectively, for simultaneously interrupting the holding circuit forthe winding 58 and establishing the circuit disposed for energizing thesignalling device 24.

If for any reason the fan 19 fails to operate or is operatinginefficiently, the windings of the transformer 1 continue to heat upresulting in a movement of the bimetal element 28 of the first controldevice 25 to a predetermined position further to the right for engagingthe switch operating member 42 to move the contact member 68 carriedthereby into engagement with the fixed contact member 69. Engagement ofthe contact members 68 and 69 efiects the establishment of a circuitpreviously described Which shunts the normally ener- 'gized Winding 58of the contactor 57 to effect the deenengization of the winding 58during substantially selfcooled operation whereby the contact members 63and 62 drop to circuit interrupting and circuit closing positions,respectively, for simultaneously interrupting the holding circuit forthe winding 58 and establishing the circuit disposed for energizing thesignal device in a similar manner to that previously described forfancooled operation.

The signal device 24 which may be energized either during self-cooledoperation or fan-cooled operation reveals to anyone in the vicinity thefact that the transformer 1 is overloadedand that the load should bereduced or .the transformer should be disconnected from the line andreplaced by one having a higher rating. If the, transformer 1 isdisconnected, the signal device 24 may be made inoperative only bymanual actuation of the start-reset switch 59 to the reset positionwhich operation establishes the circuit disposed forenergizing thewinding 58 whereby the contact members 62 and 63 are actuatedsimultaneously to effect the interruption of the signal circuit and theestablishment of the holding circuit for the winding 58, respectively.

When theload currenton the transformer 1 decreases to a safepredetermined value, the winding 32 of the relay 33 is so deenergized asto actuate the Contact mem ber 35 thereof to a circuit interruptingposition to in terrupt the holding circuit for the winding 45 of thecon-' tactor 46, thus causing the contact members 50 and 51 thereof todrop out for interrupting the energizing cir-' cuit for the fan motor 52whereby operation of the fan 19 is discontinued.

If it is found necessary to operate the fan 19 in an emergencysituation, such as, for example, in the event of failure of theoperation of the relay 33 or the bimetal element 28, or the indicatingdevice 24, or the bimetal element 128, the automatic-manual switch 38may be manually actuated to a position where it engages a fixed contactmember 72. Such actuation of the switch 38- elfects the establishment ofa circuit extending from thepoWer line conductor 36 through theconductor 37, the switch 38, the conductor 73, the winding 45 of thecon-- tactor 46 and through the conductor 47 to the line con-- ductor 48to thereby energize the winding 45 for effecting: the establishment ofthe energizing circuit for the fan motor 52.

In summary, the protective means, as disclosed provides automaticcontrol for the cooling means associated with an air-cooled transformerand for indicating predetermined load conditions of the transformerduring substantially self-cooled operation and during the operation ofthe cooling means. The first control device 25, in general, operates toinitiate operation of the fan 19 and to energize the signal device 24 inthe event that the fan 19 fails to operate or is operatinginefficiently. The second control device 125, in general, is responsiveto temperatures which are less than the temperatures to which the firstcontrol device 25 responds and operates to control the energization ofthe signal device 24 after the operation of the fan 19 has beeninitiated by the operation of the first control device 25 and the relay33. The relay 33 cooperates with the first control device 25 to maintainenergization of the fan 19 after the fan 19 has been energized by thefirst control device 25 until the load current of the transformer 1 hasdecreased to a safe predetermined value.

The apparatus and circuits embodying the teachings of this inventionhave several advantages. For example, if it is desired, a transformermay be operated under overload conditions for a considerable timewithout danger of overheating the coil assembly or windings of thetransformer. Such operation is made possible by means of the operationof the first control device 25 and the protective circuits relatedthereto to operate the fan 19 for cooling the coil assembly when theload on the transformer becomes excessive. The holding circuit for thewinding 45 of the contactor 46 is disposed for maintaining operation ofthe fan motor 52 independently of the position of the bimetal 28 toprevent a rapid cycling or hunting of the fan 19 caused by alternatingmovement of the bimetal 28, thereby reducing the switching duty on thecontact members and increasing the efliciency of the forced air cooling.If the fan 19 fails to operate or is operating ineificiently, or if theenergizing winding 58 of the contact 57 becomes deenergized for anyreason, the signal device 24 is then energized to warn of impendingdanger to or of the failure of the apparatus and remains in suchcondition until the start-reset switch 59 is manually actuated to acircuit closing position. In particular, the protective means, asdisclosed, has the additional advantage that the signal device 24 isenergized when a dangerous predetermined overload condition results inthe transformer after the fan 19 is energized and is operating normally.The latter operation of the signalling device 24 is not possible withconventional protective means of this type which in clude only a singlethermally responsive control device since the temperatures at which thesecond control device respond are less than the temperatures to whichthe first control device 25 responds.

In addition, the fan 19 may be turned on at any time 11 if so desired bymanual actuation of the automaticmanual switch 38. This feature of theprotective system or means provides for operation of the fan 19 in theevent of failure of the bimetal element 28, the relay 33, or any part ofthe circuit in association with the circuit operable upon such actuationof the switch 38.

Since numerous changes may be made in the abovedescribed apparatus andcircuits, and different embodiments of the invention may be made withoutdeparting from the spirit thereof, it is intended that all the mattercontained in the foregoing description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

I claim as my invention:

1. In an air-cooled transformer provided with a coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly and to the heating caused by the currentflowing in said coil assembly, said first control device including firstand second contact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current fiow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, first means disposed to be energized to effectthe operation of said cooling means only after said relay is energizedand the first contact member of said first control device is closed,said relay when energized cooperating with said first means tothereafter effect the energization of said cooling means independentlyof said first control device and when deenergized cooperating with saidfirst means to deenergize said cooling means, a signalling meansdisposed for operation for indicating a predetermined load condition ofsaid transformer, second means disposed for operation in response to theclosing of said second contact member of said first control device toeffect operation of said signalling means, said second control deviceincluding first and second contact members arranged to open and closerespectively at different degrees of loading of said transformer attemperatures less than the temperatures required for the operation ofsaid first control device and a contactor disposed to be energized onlywhen the first contact member of said second control device has closedafter said first means has effected the operation of said cooling means,said contactor when energized cooperating with the second contact memberof said second control device to effect operation of said second meansand said signalling means in response to the closing of said secondcontact member of said second control device after said first means haseffected the operation of said cooling means and said first contactmember of said second control device has closed.

2. In an air-cooled transformer provided with a coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly and to the heating caused by the currentflowing in said coil assembly, said first control device including firstand secondcontact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current flow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, first means disposed to be energized to effectthe operation of said cooling means only after said relay is energizedand the first contact member of said first control device is closed,said relay when energized cooperating with said rst means to thereaftereffect the energization of said cooling means independently of saidfirst control device and when deenergized cooperating with said firstmeans to deenergize said cooling means, a signalling means dis-, posedfor operation for indicating a predetermined load; condition of saidtransformer, second means disposed for operation in response to theclosing of said second contact member of said first control device toeffect operation of said signalling means, said second control devicein-. cluding first and second contact members arranged to open and closerespectively at different degrees of loading of said transformer attemperatures less than the temperatures required for the operation ofsaid first control device and a contactor disposed to be energized onlywhen the first contact member of said second control device has closedafter said first means has effected the operation of said cooling means,said contactor when energized cooperating with the second contact memberof said second control device to effect operation of said second meansand said signalling means in response to the closing of said secondcontact member of said second control device after said first means haseffected the operation of said cooling means and said first contactmember of said second control device has closed, and

switch means disposed to be manually operated to control theenergization of said first means independently ofthe energization ofsaid relay and the actuation of said first contact member of said firstcontrol device andto effect the operation of said cooling means.

3. In an air-cooled transformer provided with a coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly and to the heating caused by the currentflowing in said coil assembly, said first control device including firstand second contact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current flow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, first means disposed to be energized to effectthe operation of said cooling means only after said relay is energizedand the first contact member of said first control device is closed,said relay when energized cooperating with said first means tothereafter effect the energization of said cooling means independentlyof said first control device and when deenergized cooperating with saidfirst means to deenergize said cooling means, a signalling meansdisposed for operation for indicating a predetermined load condition ofsaid transformer, a normally energized signalling contactor disposed foroperation in response to the actuation of said second contact member ofsaid first control device to effect the operation of the signallingmeans, said second contact member of said first control device beingdisposed when actuated to effect the deenergization of said signallingcontactor to thereby effect the operation of said signalling meansindependently of. said first control device, said second control deviceincluding first and second contact members arranged to open and closerespectively at different degrees of loading of said transformer attemperatures less than the temperatures required for the operation ofsaid first control device and a contactor disposed to be energized onlywhen the first contact member of said second control device has closedafter said first means has effected the operation of said cooling means,said contactor when energized cooperating with the second contactmember.

of said second control device to effect operation of said second meansand said signalling means in response to the closing of said secondcontact member of said second control device after said first means haseffected the operation of said cooling means and said first contact member of said second control device has closed.

4. In an air-cooled transformer provided with a coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly anzl to the heating caused by the currentflowing in said coil assembly, said first control device including firstand second contact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current flow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, first means disposed to be energized to effectthe operation of said cooling means only after said relay is energizedand the first contact member of said first control device is closed,said relay when energized cooperating with said first means tothereafter effect the energization of said cooling means independentlyof said first control device and when deenergized cooperating with saidfirst means to deenergize said cooling means, a signalling meansdisposed for operation for indicating a predetermined load condition ofsaid transformer, a normally energized signalling contactor disposed foroperation in response to the actuation of said second contact member ofsaid first control device to effect the operation of the signallingmeans, said second contact member of said first control device beingdisposed when actuated to efiect the deenergization of said signallingcontactor to thereby effect the operation of said signalling meansindependently of said first control device, said second control deviceincluding first and second contact members arranged to open and closerespectively at different degrees of loading of said transformer attemperatures less than the temperatures required for the operation ofsaid first control device and a contactor disposed to be energized onlywhen the first contact member of said second control device has closedafter said first means has effected the operation of said cooling means,said contactor when energized cooperating with the second contact memberof said second control device to effect operation of said second meansand said signalling means in response to the closing of said secondcontact member of said second control device after said first means haseffected the operation of said cooling means and said first contactmember of said second control device has closed, and switch meansdisposed to be manually actuated for operation to energize thesignalling contactor to effect the discontinuation of operation of thesignalling means.

5. In an air-cooled transformer provided with coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly and to the heating caused by the currentflowing in said coil assembly, said first control device including firstand second contact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current flow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, first means disposed to be energized to effectthe operation of said cooling means only after said relay is energizedand the first contact member of said first control device is closed,said relay when energized cooperating with said first means tothereafter effect the energization of said cooling means independentlyof said first control device and when deenergized cooperating with saidfirst means to deenergize said cooling means, a signalling meansdisposed for operation for indicating a predetermined load condition ofsaid transformer, second means disposed for operation in response to theclosing of said second contact member of said first control responsivedevice to effect operation of said signalling means, said second controldevice including first and second contact members arranged to open andclose respectively at different degrees of loading of said transformerat temperatures less than the temperatures required for the operation ofsaid first control device and a contactor disposed to be energized onlywhen the first contact member of said second control device has closedafter said first means has effected the operation of said cooling means,said contactor when energized cooperating with the second contact memberof said second control device to effect operation of said second meansand said signalling means in response to the closing of said secondcontact member of said second control device after said first means haseffected the operation of said cooling means and said first contactmember of said second control device has closed, and switch meansdisposed to be manually operated to control the energization of saidfirst means to effect the operation of said cooling means independentlyof said relay and the actuation of said first contact member of saidfirst control device.

6. In an air-cooled transformer provided with a coil assembly, incombination, cooling means disposed for operation to effect the coolingof the transformer, first and second thermally responsive controldevices disposed to be responsive to both the temperature of the airrising from said coil assembly and to the heating caused by the currentflowing in said coil assembly, said first control device including firstand second contact members arranged to close at different degrees ofloading of said transformer, a relay disposed to be energized inresponse to a predetermined value of current flow in said coil assemblyand to be deenergized when the current flow decreases to a value belowsaid predetermined value, a cooling means contactor disposed to beenergized to effect the operation of said cooling means only after saidrelay is energized and the first contact member of said first controldevice is closed, said relay when energized cooperating with said firstmeans to thereafter effect the energization of said cooling meansindependently of said first control device and when deenergizedcooperating with said first means to deenergize said cooling means, asignalling means disposed for operation for indicating a predeterminedload condition of said transformer, sec ond means disposed for operationin response to the closing of said second contact member of said firstcontrol responsive device to effect operation of said signalling means,said second control device including first and second contact membersarranged to open and close respectively at different degrees of loadingof said transformer at temperatures less than the temperatures requiredfor the operation of said first control device and a contactor disposedto be energized only when the first contact member of said secondcontrol device has closed after said first means has effected theoperation of said cooling means, said contactor when energizedcooperating with the second contact member of said second control deviceto effect operation of said second means and said signalling means inresponse to the closing of said second contact member of said secondcontrol device after said first means has effected the operation of saidcooling means and said first contact member of said second controldevice has closed.

7. In electrical apparatus, the combination of a housing, a transformercore and coil assembly disposed therein, air-cooling means disposed foroperation to effect the cooling of the coil assembly, a signalling meansdisposed for operation for indicating a predetermined load operatingcondition of the transformer, a first and a second control device eachdisposed to be operated in response to predetermined temperatures of aircurrents rising from the coil assembly and predetermined heating effectsof current flowing through the coils of the transformer, each of saidcontrol devices including a thermally responsive means disposed formovement through two switching positions in response to variations insaid temperatures and heating effects, the thermal responsive means ofsaid second control device being arranged to respond to lowertemperatures than the thermal responsive means of said first controldevice, a relay disposed to be energized in response to a predeterminedflow of current through the coils and to be deenergized when the currentflow through the coils decreases below said predetermined flow ofcurrent, a first contact member of said first control device disposed tobe actuated to a circuit closing position upon the occurrence of apredetermined movement of the thermally responsive means of said firstcontrol device to one of said switching positions, a first contactordisposed to be energized to efiect the operation of the cooling meansonly after said relay is energized and said first contact member isactuated to circuit closing position, the relay when energizedcooperating with said contactor to thereafter effect the energization ofsaid cooling means independently of the movement of the thermallyresponsive means of the first control device and when deenergizedcooperating with said contactor to deenergize said cooling means, asecond contact member of said first control device disposed to beactuated to a circuit closing position upon the occurrence of a furtherpredetermined movement of the thermally responsive means of said firstcontrol device to the other of said switching positions, a signallingcontactor disposed for operation in response to actuation of said secondcontact member of said first control device to effect the operation ofthe signalling means, a first contact member of said second controldevice disposed to be actuated to a circuit opening position upon theoccurrence of a predetermined movement of the thermally responsive meansof said second control device to one of said switching positions, asecond contact member of said second control device disposed to beactuated to a circuit closing position upon the occurrence of a furtherpredetermined movement of the thermally responsive means of said secondcontrol device, and a second contactor disposed to be deenergized inresponse to actuation of the first contact member of said second controldevice, said signalling contactor disposed for operation in response toactuation of said second contact member of said second control deviceafter said first contact member of said second control device has beenactuated first to a circuit opening position and ret urnedto a circuitclosing position following the energization of said first contactor toeifect the operation of said cooling means.

8. In electrical apparatus, the combination of a housing, a transformercore and coil assembly disposed therein, air-cooling means disposed foroperation to eifect the cooling of the coil assembly, a signalling meansdisposed for operation for indicating a predetermined load operatingcondition of the transformer, a first and a second control device eachdisposed to be operated in response to predetermined temperatures of aircurrents rising from the coil assembly and predetermined heating effectsof current flowing through the coils of the transformer, each 16 of saidcontrol devices including a thermally responsive means disposed formovement through two switching positions inresponse to variations insaid temperatures and heating eflects, the thermal responsive means ofsaid second control device being arranged to respond to lowertemperatures than the thermal responsive means of said first controldevice, a relay disposed to be energized in response to a predeterminedflow of current through the coils and to be deenergized when the currentflow through the coils decreases below said predetermined flow ofcurrent, a first contact member of said first control device disposed tobe actuated to a circuit closing position upon the occurrence of apredetermined movement of the thermally responsive means of said firstcontrol device to one of said switching positions, a first contactordisposed to be energized to effect the operation of the cooling meansonly after said relay is energized and said first contact member isactuatedto' circuit closing position,

the relay when the energized cooperating with said' con ta'ctor tothereafter efiect' the energization of said cooling means independentlyof the movement of the thermally responsive means of the first controldevice and when deenergized cooperating with said contactor todeenergize said cooling'me'ans, a second contactmember of said firstcontrol device disposed to be actuated to a circuit closing positionupon the occurrence of a further predetermined movement of the thermallyresponsive means of said first control device to the other of saidswitching positions, a signalling contactor disposed for operation inresponse to actuation of said second contact member of said firstcontrol device to effect the operation of the signalling means, a firstcontact member of said second control device disposed to be actuated toa circuit opening po'sition upon the occurrence of a predeterminedmovement of the thermally responsive means of said second control deviceto one of said switching positions, a second contact member of saidsecond control device disposed to be'actuate'd to a circuit closingposition upon the occurrence of a further predetermined movement of thethermally responsive means of said second control device, and a secondcontactor disposed to be deenergized in response to actuation of thefirst contact member of said second control device, said signallingcontactor disposed for operation in response to actuation of said secondcontact member of said second control device after said first contactmember of said second control device has been actuated first to acircuit opening position and returned to a circuit closing positionfollowing the energization of said first contactor to effect theoperation of said cooling means, and switch means disposed to bemanually ac-' tuated for operation to cause said signalling contactor toeffect the discontinuation of operation of said signalling means.

No references cited.

